🚀 go-pugleaf

In article <1992Sep8.202500.27325@oswego.Oswego.EDU> nacs4160@Oswego.EDU ( Marc F. Houde) writes:
 I'm looking for programs to run a stepper motor accurately at high speeds. It 
 is to be used for a project in holography. Please send any info to:

Three years ago I was also looking to control steppers. At the time I
had varying velocity demands coming in to a drive motor, simple I
thought.  Open loop positioning, so all you have to do is work out from
the velocity demand what the step interval should be.

When implemented things actualy looked harder. The system had a fixed
time quantisation interval (tick). This tick quantisation could be
quite significant compared to the step period.

An addition all this had to be done very quickly, the only time was on
the interupt period of a simple 8 bit microprocessor. This made me
think of Breshenham's line draw algorithem. Fast, integer only,
naturally fitting to a quantisation problem.

The stepper motor problem required that the velocity (gradient) could
be varied on the fly, and could also be +ve, and -ve. Two descision
variables are required to cope with this modified case. The big
advantage of this was the algorithm has no residual error. If the
velocity required doesn't quantise in time exactly the output will
still run at the correct velocity 'on average'. The residual error is
carried over to the next time step and added to whatever the new
velocity is.  Formally: The stepper will be exactly at the same
position as the integral of the velocity demands to get position.

At the time I did a quick literature survey to see if others had
applied a Breshenham like method, but nothing came up. Has anyone else
done something similar? Anyone interested in the algorithm?


--
Michael Stevens, Robotics Research Group,Dept of Engineering Science,Oxford,UK
INTERNET: michael@robots.oxford.ac.uk